Proprioceptive accuracy after uni-joint and multi-joint patterns of arm-raising movements directed to overhead targets.

Aim: To determine the effect of arm-raising pattern on upper limb proprioceptive accuracy for movements made to overhead targets.

Materials and methods: Sixteen healthy young adults were tested in standing with arms at the sides, made dominant arm-raising movements to an unseen overhead stop, randomly placed at one of five different overhead targets. Movements were made either as a uni-joint shoulder flexion movement in an arc, or as an unconstrained arm raising that was a series of multi-joint movements involving the shoulder, elbow, and wrist.

Results: Overall proprioceptive accuracy for discrimination between the five unseen overhead targets was not different after arm-raising with either a uni-joint or mult-joint pattern (F_{1, 15} = 0.50, p = 0.49, partial η² = 0.03). Better performers with one pattern also tended to perform well with the other (r = 0.70, p = 0.003). Trend analysis across the 4 pairwise scores for discriminations between the target positions (171.8°-173.6°, 173.6°-175.4°, 175.4°-177.2°, and 177.2°-179.0°) showed worsening discrimination towards the more distant targets (F_{1, 15} = 8.44, p = 0.01, partial η² = 0.36). However, this linear trend of falling discrimination accuracy was not different between the two movement patterns (p = 0.27).

Conclusion: Proprioceptive accuracy did not differ between simple uni-joint and more complex multi-joint arm-raising movement patterns, and the further the extent of the overhead target movement, the worse proprioceptive discrimination sensitivity for both movement patterns. Upper limb proprioceptive accuracy was therefore movement extent dependent, but movement pattern independent.